512 research outputs found
Inflation From Symmetry Breaking Below the Planck Scale
We investigate general scalar field potentials \hbox{}
for inflationary cosmology arising from spontaneous symmetry breaking. We find
that potentials which are dominated by terms of order with \hbox{} can satisfy observational constraints at an arbitrary symmetry breaking
scale. Of particular interest, the spectral index of density fluctuations is
shown to be independent of the specific form of the potential, depending only
on the order of the lowest non-vanishing derivative of near its
maximum. The results of a model with a broken symmetry illustrate
these features.Comment: Submitted to Phys. Rev. Letters. 7 Pages, REVTeX. No figure
Attractor Solutions in Tachyacoustic Cosmology
We study the dynamical stability of "tachyacoustic" cosmological models, in
which primordial perturbations are generated by a shrinking sound horizon
during a period of decelerating expansion. Such models represent a potential
alternative to inflationary cosmology, but the phase-space behavior of
tachyacoustic solutions has not previously been investigated. We numerically
evaluate the dynamics of two non-canonical Lagrangians, a cuscuton-like
Lagrangian and a Dirac-Born-Infeld Lagrangian, which generate a scale-invariant
spectrum of perturbations. We show that the power-law background solutions in
both cases are dynamical attractors.Comment: Some references and comments added. Accepted for publication in
Physical Review
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